Traditionally, in the office equipment context, to make a copy of an original document, a light lens xerographic copier was used. In these machines, the image of the original is focused on an area of a photoreceptor, which is subsequently developed with a toner. The developed image on the photoreceptor is then transferred to a copy sheet to create a permanent copy of the original.
In recent years, there has been made available what are known as digital scanners. A digital scanner performs some of the same functions as a light lens copier such as illumination of the original document as well as focusing the image through lenses and mirrors (via an optical system). In a digital scanner, however, the original image is typically focused onto one or more linear arrays of photosensitve surfaces of an image sensor (e.g., a charged coupled device). The array of photosensitve surfaces converts the original image into a set of analog signals that can then be further processed into digital signals.
These digital signals can be temporarily retained in a memory and then eventually used to operate a printing apparatus when it is desired to print copies of the original. In some scanners, the digital signals may also be used to create facsimiles or electronic mail (e-mail) for transmission to external computing devices.
One common type of scanner is the flat bed scanner. Flat bed scanners are conventionally provided with a horizontal, flat and transparent platen and an opaque platen cover. In order to scan a page, a user can place the page over a predetermined area on the upper surface of the platen. This predetermined area is referred to herein as the xe2x80x9cfixed page scan areaxe2x80x9d.
After the page is placed over the fixed page scan area, the user then typically closes the cover over the page and initiates the scanning operation. During the scanning operation, the document is illuminated and the image sensor is optically exposed to each section of the page through the fixed page scan area on the platen. In general, this type of scan operation is referred to herein as a xe2x80x9cfixed page scan operationxe2x80x9d in order to indicate that the page being scanned is maintained in a fixed position on the upper surface of the platen during the scanning process.
A flat bed scanner may also be provided with an automatic document feeder (ADF). The ADF automatically feeds pages, one by one, over a second predetermined area on the upper surface of the platen. This second predetermined area is referred to herein as the xe2x80x9cADF scan areaxe2x80x9d . In order to use the ADF to scan a page, a user first places the page in the input tray of the ADF and then initiates a scanning operation. During the scanning operation, the ADF moves the page over the ADF scan area as the image sensor is optically exposed to each section of the page (through the ADF scan area). It is noted that as the page is moved over the ADF scan area, the page may or may not physically contact the platen. For purposes of this application, this type of scan operation is referred to herein as an xe2x80x9cADF scan operationxe2x80x9d.
During an ADF scan operation a problem can arise if a left over page from a previous fixed page scan operation covers, or partially covers, the ADF scan area. If such a condition exists, the page (ADF page) being fed by the ADF may be improperly scanned as the left over page can block the optical path between the ADF page and the image sensor. This problem is compounded if the scanner is being used to FAX or e-mail the page. In such as case, the user may not have timely feedback that the ADF scan operation was not properly performed.
Prior solutions to this problem include incorporating into the flat bed scanner a page feed mechanism. Prior to starting an ADF scan operation, the page feed mechanism clears the ADF scan area of any pages left on the upper surface of the platen. Unfortunately, adding a page feed mechanism can be unduly costly and adds complexity to the scanner. In addition, the components in the page feed mechanism may fail over time. As a result, this solution can decrease scanner reliability and increase scanner service cost.
A second solution to this problem is to provide a sensor in the scanner for sensing the opening and closing of the platen cover. For example, if the scanner senses that the platen cover has been opened and then closed, it is assumed that a left over page exists on the platen. If the user then attempts to perform an ADF scan operation, the scanner notifies the user that a page may be present on the platen. If, however, the cover is opened a second time (presumably to remove the page from the platen) prior to an ADF scan operation it is assumed that the page has been removed from the platen. The problem with this solution is that these assumptions can be wrong. Thus, this second solution is often unreliable. Also, the additional sensors add cost and complexity to the scanner.
Accordingly, there is a need for a way to ensure a page is not covering the ADF scan area on the platen of a flat bed scanner prior to the scanner performing an ADF scan operation that is inexpensive, does not add complexity to the scanner and is reliable.
In one aspect of the present invention, apparatus is provided that can be used to detect whether a page is present on the platen of a flat bed scanner. Importantly, the apparatus is inexpensive, does not add significant complexity to the scanner and is reliable.
In one embodiment, the apparatus includes an indicium (i.e., a machine readable object or mark) and a sensor. The sensor includes one or more photosensitive surfaces for detecting the indicium when the photosensitive surface and indicium are in optical communication. The indicium and the sensor are positioned so that an optical path, passing through an area on the platen, exists between the one or more photosensitive surfaces and the indicium if the area is uncovered by a page. In operation, if the sensor fails to detect the indicium, then the sensor generates a signal indicating that a page is present on the platen. Preferably, the sensor is the same sensor (e.g., a CCD array) used by the scanner to scan a page.
The apparatus just described can be used to detect whether a page is present on the platen (and possibly covering the ADF scan area on the platen) prior to the scanner performing an ADF scan operation. If a page is detected, the apparatus can be adapted to notify the user.
In another embodiment, a flat bed scanner is provided. The scanner includes a platen and an indicium. The platen includes an upper transparent surface having a fixed page scan area over which a first page can be placed for scanning. The transparent surface also includes a page detect area which is located at least partially within the fixed page scan area. The indicium is positioned so as to face the page detect area. The scanner further includes a scanning mechanism that is operative to determine if a page is present on the transparent surface by scanning through the page detect area. If, during this scanning operation, the scanning mechanism fails to detect the indicium then a signal is generated indicating a page is present on the platen.
In yet another embodiment, the present invention is implemented as a method that may be performed to determine the presence of a page on the platen of a flat bed scanner. The method includes providing an indicium above an area on the platen. The method further includes scanning through this area to determine if the indicium can be detected. If the indicium is not detected, then it is determined that a page is present on the platen. The method just described may be used by the scanner to determine if a page is present on the platen prior to the scanner performing an ADF scan operation.
It should be understood that the foregoing summary and the following detailed description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the present invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.